pilomatricoma

Definition: Pilomatricoma (pilomatrixoma) is a benign tumor more frequently found on the head, neck and shoulders of young adults and children.

Histologically it shows nests of basaloid cells producing trichilemmal-type keratin and ghost cells - enlarged eosinophilic epithelial cells with eosinophilic cytoplasm and without a nucleus. It may also show a foreign body reaction, calcification or ossification.

Aggressive and malignant variants are diagnosed by cytologic atypia and invasion.

Digital cases

 JRC:10845 : Pilomatrixoma.
 JRC:10847 : Pilomatrixoma.
 pathxchange #2207.

Images

 https://twitter.com/mreyesm/status/724706492931276800
 https://twitter.com/stubob/status/738584478063284226

Variants

 pilomatrixoma with only germinative-matrical cells (see photos) ((with the passage of time, the number of basaloid cells decreases progressively, eventually to be replaced by ghost cells)
 lymphangiectatic variant of pilomatricoma (15324397)
 pilomatricoma with a bullous appearance (15268712)

Differential diagnosis

 basal cell carcinoma
 pilomatrical carcinoma
 melanocytic matricoma

Etiology

 some cases of pilomatrixoma are caused by mutation in the beta-catenin gene (CTNNB1) (MIM.116806) (12575848, 11472567, 11004631, 10192393)

Epidemiological forms

 multiple pilomatricomas (pilomatricomatosis or pilomatrixomata) (8747580, 12702091)
 familial pilomatricomas (14984583, 12702091)

Associations

 multiple pilomatricomas and myotonic dystrophy (10434894, 3175462, 11978577, 8891827)
 multiple pilomatricomas and trisomy 9 (11834859)
 peripheral schannoma (15640970)
 multiple pilomatricomas in Rubinstein-Taybi syndrome (15324407, 8170843)
 Turner syndrome (10640845)

See also

 cutaneous lesions
 cutaneous tumors

• cutaneous adnexal tumors